Water displacing and rust preventive compositions



United States Patent 3,383,328 WATER DISPLACING AND RUST PREVENTEVE COMPOSITIONS Hayward R. Baker, Silver Spring, Md., and Paul B. Leach, Woodlawn Manor, Fairfax County, Va., assignors to the United States of America as represented by the Secretary of the Navy No Drawing. Filed Apr. 4, 1966, Ser. No. 540,098 3 Claims. (Cl. 252390) This invention relates to Water-displacing rust-preventative compositions.

Gas turbine engines operating in aircraft near the surface of the ocean ingest significant amounts of salt water spray. This sea water is evaporated by the intake high velocity air to leave dense salt deposits on the turbine compressors. The accumulated salt leads to rusting of the 403 and 410 stainless steel compressor blades, especially where they fit into the high strength aluminum alloy slip rings.

To minimize adverse effects of salt deposits on compressors of aircraft gas turbine engines which are exposed to salt water contamination in operation, it is the practice in after-flight servicing of the aircraft to periodically flush the compressors with water during cycling of the engines, start the engines for a short period high velocity air blow out of the wash water, and then to spray a preservative composition into the compressors during coastdown to retard rusting during periods of nonoperation of the engines. The compressors are then capped.

The preservative composition which has been used is not satisfactory from the standpoint of the length of duration of the rust protection provided to the compressors. In general, the duration of the rust protection period is only a few days, whereas it is obviously desirable that rust protection be provided for considerably longer periods of nonoperation of the engines, for example, two weeks to a month.

The short protection period afforded to the compressors by the priorly used protective composition is due to the inability of the composition to displace water from solid surfaces, in particular salt water lying in crevices between the compressor blades at their junction with the shaft. All the washwater is not removed from the compressors by the blowing out operation. Water remains at the base of the compressor blades and with salt residue form small pools of salt water at these sites. There is no corrosion inhibitor known which can effectively combat the activity of saltwater to corrode metals. Protection of the steel surface of the compressors requires displacement of the salt water from the surfaces and the formation thereon of a film of a corrosion inhibitor which serves as a barrier to access or return of the saltwater to the steel surfaces. The priorly used protective composition cannot do this, since it does not displace water from solid surfaces whereby the corrosion inhibitor can reach the steel surface to become adhered thereto.

It is the general object of the present invention to improve the rust protection provided in the aforesaid afterflight servicing of compressors of gas turbine engines which in operation have been exposed to ingestion of salt water spray. It is a particular object to provide new waterdisplacing, rust-preventive compositions.

The above and other objects are achieved in the compositions of the invention and their use as water-displacing, rust-preventive agents in the aforesaid after-flight servicing of compressors of gas turbine engines.

The new compositions are clear fluids which contain a small amount of Water, a vapor phase corrosion inhibitor, a complex addition salt of a primary alkyl monoamine 3,383,328 Patented May 14, 1968 having from 12 to 22 carbon atoms and aliphatic polybasic acids which are a mixture of the C dimer and C trimer of a C unsaturated fatty acid of the group, oleic, linoleic and linolenic acids, and a light petroleum lubricating oil in a volatile solvent which is a mixture of isopropanol and a petroleum hydrocarbon of the Stoddard solvent type.

The primary alkyl amines which may be used for the formation of the complex addition salt in the compositions are straight chain primary alkyl monoamines con taining from 12 to 22 carbon atoms, for example, laurylamine, myristylamine, palmitylamine, stearylamine arachidylamine and behenylamine, and primary tertiary alkylamines of the group C H NH to C H NH The latter are commercially available under the tradename Primene JM-T.

The mixed dimer and trimer unsaturated polybasic acids which may be used for the formation of the complex addition salt in the compositions contain the C dimer acid in predominant amounts. Suitably they are composed essentially of about to by weight of the C dimer acid and from about 25 to 5% of the trimer acid. The dimer acid is a dicarboxylic acid and the trimer acid a tricarboxylic acid. Various dimer and trimer acid mixtures are available commercially under the tradename of Empol 1014, 1016, 1018, 1022 and 1024 and under the tradename of Santolene C.

The fluid compositions of the invention comprise from about 39.5 to 48.5% by weight of isopropanol, from about 3.5 to 4.5% by weight of water, from about 5.5 to 6.5% by weight of the primary alkyl monoamine in the form of a complex addition salt with from about 10.8 to 13.2% by weight of the mixed C dimer and C trimer of the C unsaturated fatty acid, from about 4.5 to 5.5% by weight of dicyclohexyl ammonium nitrite, from about 13.5 to 16.5% by weight of a volatile petroleum hydrocarbon of the Stoddard solvent type and from about 12.5 to 15.5% of a light petroleum lubricating oil.

The isopropanol has a duel role in the compositions, serving as the princi al solvent and also as the water displacing agent. From the standpoint of lower cost, the function of solvent is shared by the isopropanol with an amount of a petroleum hydrocarbon of the Stoddard solvent type which does not interfere with the water-displacing activity of the compositions. A suitable ratio of the alcohol to the petroleum hydrocarbon solvent is about 3:1 by weight. Petroleum hydrocarbons of the Stoddard solvent type meet the requirements of Type I, Fed. Spec. RS. 66 lb. They have a flash point minimum of F. and vapor pressures at room temperature near those of isopropanol such that there is practical match in their volatility in use of the compositions for providing corrosion protection to the compressors.

Suitable light petroleum lubricating oils for use in the compositions are those which correspond to Spec. Mil.- 060'8lb, Grade 1005. These lubricating oils have a viscosity of 5 cps. min. at 100 F. and a viscosity of 2600 cps. max. at 65 F. The function of the light lubricating oil is to protect against a dry, hard or brittle condition of the corrosion protection film at the base of the variable pitch blades of the compressor which would interfere with movement thereof in subsequently operating the gas turbine engine.

Preparation of the compositions of the invention may be accomplished by first dissolving the primary alkyl monoamine in the isopropanol which contains the water for the composition, either by addition to anhydrous isopropanol or by virtue of the use of a 91 to 93% technical grade isopropanol. To this isopropanol solution is then added with stirring and in the following order: the

vapor phase inhibitor, which is dicyclohexyl ammonium nitrite, the mixture C dimeric and C trimeric unsaturated polybasic acids, the volatile petroleum hydrocarbon of the Stoddard type and then the light petroleum lubricating oil. Formation of the complex addition salt takes place in the composition on addition of the mixed dimer and timer acids to the isopropanol solution of the primary alkyl monoamine.

Application of the new fluid compositions for rust protection of compressors of gas turbine engines which have been exposed to contamination by salt water spray is carried out in accordance with the procedure of the aforesaid after-flight servicing of the gas turbine engine compressors of aircraft. The fluid composition is sprayed into the compressors on engine coastdown following the air blowing out of wash water from the flushing operation. Applied in the foregoing after-flight servicing to compressors of gas turbine engines, the new compositions have the capacity to provide protection to the compressors against rusting by salt water attack for periods of two weeks to a month or more during the nonoperation of the engines.

Sprayed into the compressors of gas turbine engines after the flash washing and air blowing out operations thereon, the new fluid compositions will function to quickly displace salt water from the crevices between the blades and at other sides therein and cover practically the entire surface area of the compressors with an adsorbed film of the complex addition salt which is at least one molecule in thickness. This film is of a soft waxy consistency and hydrophobic in nature and is a barrier to return of the displaced salt water to the steel surface and resultant corrosion of the steel surface by salt water. A containued deposition of the complex addition salt from the syrayed composition onto the hydrophobic film builds up the thickness of the film and strengthens it by bulk effect.

In operation of the compositions as a water-displacing and rust preventive, the isopropanol penetrates through the films or small pools of salt water to reach the substrate steel surface of the compressor and displace the salt water therefrom. At the same time, the isopropanol and the volatile hydrocarbon solvent are undergoing evaporation which causes some of the complex addition salt to leave the composition and become deposited on the steel surface from which the salt water has been displaced. This deposit of complex addition salt being polar in nature is adhorbed to the steel surface. Part of the displaced salt water will be carried off by the evaporating isopropanol. The remainder will stand on the hydrophobic film and eventually evaporate in the ambient air. The isopropanol and the petroleum hydrocarbon of the Stoddard solvent type will evaporate rather quickly from the compressor surfaces. The light petroleum oil will remain after evaporation of the isopropanol and Stoddard type solvent to act as a softener for the hydrophobic film of the complex addition salt.

The dicyclohexyl ammonium nitrite will vaporize in the compressors which are capped after having been sprayed with the composition. The vaporized inhibitor will reach and be absorbed to surface areas not covered by the film of the complex addition salt to assure a maximum of rust protection to the compressors.

The invention is further illustrated by the following example of a preferred composition which is prepared in the manner above described. The composition is defined in terms of the compoents as they are added in forming it.

Component: Percent by wt. Alamine H 26D 1 6 isopropanol (8% water) 48 Dicyclohexyl ammonium nitrite 5 Santolene C 12 Stoddard type solvent 15 Light Petroleum Lub. Oil 14 Mixed palmityl and stearylamines in the ratio of 30:70

by weight.

Mixed Cw dimer and C54 trimer of linolenic acid in which the C36 dimer predominates.

The coating on the compressor surfaces which is provided by the new compositions will burn without leaving an ash. This is a further advantage of the new compositions since the coating on the compressors is eventually burned by the heat developed in the gas turbine engines when the aircraft are again put into operation.

While the invention has been described herein with reference to a specific embodiment thereof the same is intended by way of illustration rather than in limitation except as may be defined in the appended claims.

What is claimed and desired to be secured by Letters Patent of the United States is:

1. A fluid composition which is a solution comprising from about 39.5 to 48.5% by weight is isopropanol, from about 3.5 to 4.5% by weight of water, from about 5.5 to 6.5% by weight of a primary alkyl amine of the group consisting of straight chain primary alkyl monoamines having from 12 to 22 carbon atoms and tertiary alkyl primary monoamines having from 18 to 22 carbon atoms, from about 10.8 to 13.2% by weight of the mixed C dimer and C timer of a C unsaturated fatty acid of the group consisting of oleic, linoleic and linolenic acids in which the C dimer predominates, said primary alkylamine and said mixed C dimer and C timer being present as a complex addition salt, from about 4.5 to 5.5% by weight of dicyclohexyl ammonium nitrite, from about 13.5 to 16.5% by weight of a volatile petroleum hydrocarbon of the Stoddard solvent type and from about 12.5 to 15.5% by weight of a light petroleum lubricating oil.

2. A composition as defined in claim 1, wherein the primary alkyl amine is a mixture of palmityl and stearylamines in the weight ratio of about 30:70.

3. A composition as defined in claim 1, wherein the mixed C dimer and C triiner of the C unsaturated fatty acid contains from about to by Weight of the C dimer and from about 25 to 5% by weight of the C54 trimer.

References Cited UNITED STATES PATENTS 2,602,780 7/1952 Zisman et al. 252-73 2,647,839 I 8/1953 Zisman et a1 252-396 X 2,943,058 6/1960 Cook 252153 3,138,558 6/1964 Baker et al. 252395 FOREIGN PATENTS 1,165,379 3/1964 Germany.

OTHER REFERENCES Tertiary-Alkyl Primary Amines, Rhom and Haas Company, December 1952.

LEON D. ROSDOL, Primary Examiner.

I. GLUCK, Assistant Examiner. 

1. A FLUID COMPOSITION WHICH IS A SOLUTION COMPRISING FROM ABOUT 39.5 TO 48.5% BY WEIGHT IS ISOPROPANOL, FROM ABOUT 3.5 TO 4.5% BY WEIGHT OF WATER, FROM ABOUT 5.5 TO 6.5% BY WEIGHT OF A PRIMARY ALKYL AMINE OF THE GROUP CONSISTING OF STRAIGHT CHAIN PRIMARY ALKYL MONOAMINES HAVING FROM 12 TO 22 CARBON ATOMS AND TERTIARY ALKYL PRIMARY MONOAMINES HAVING FROM 18 TO 22 CARBON ATOMS, FROM ABOUT 10.8 TO 13.2% BY WEIGHT OF THE MIXED C36 DIMER AND C54 TIMER OF A C18 UNSATURATED FATTY ACID OF THE GROUP CONSISTING OF OLEIC, LINOLEIC AND LINOLENIC ACIDS IN WHICH THE C36 DIMER PREDOMINATES, SAID PRIMARY ALKYLAMINE AND SAID MIXED C36 DIMER AND C54 TIMER BEING PRESENT AS A COMPLEX ADDITION SALT, FROM ABOUT 4.5 TO 5.5% BY WEIGHT OF DICYCLOHEXYL AMMONIUM NITRITE, FROM ABOUT 13.5 TO 16.5% BY WEIGHT OF A VOLATILE PETROLEUM HYDROCARBON OF THE STODDARD SOLVENT TYPE AND FROM ABOUT 12.5 TO 15.5% BY WEIGHT OF A LIGHT PETROLEUM LUBRICATING OIL. 